An elevated aldosterone-renin ratio (ARR) suggests primary aldosteronism. The next step, when confirmation is needed, is to show that aldosterone secretion is autonomous, meaning it does not suppress appropriately after sodium or mineralocorticoid loading.

Therefore, the following are confirmatory tests for primary aldosteronism:

In primary aldosteronism, aldosterone remains inappropriately high despite these suppression maneuvers.

Metyrapone stimulation test is not used for this purpose. Metyrapone blocks cortisol synthesis, lowering cortisol feedback and thereby testing whether the hypothalamic-pituitary axis can raise ACTH and 11-deoxycortisol. It is used mainly to assess central (secondary) adrenal insufficiency, not hyperaldosteronism.

So the simple exam rule is:

A current review supports the use of saline infusion, oral sodium loading, fludrocortisone suppression, and captopril challenge as confirmatory approaches for primary aldosteronism, as summarized in this AHA review. The textbook library also lists saline infusion and fludrocortisone suppression as confirmatory testing methods: Campbell-Walsh Wein Urology, “Testing for Aldosterone Hypersecretion,” lines 148-149.